Hydronic Zone Valves

Zone Valves Play an Important Role in your Hot Water Heating System

By Mark J. Donovan




Is your hot water heating system continuously running or not working at all? When you turn down the thermostat does hot water continue to flow through your hot water heating system? If so, it is possible that you have a failed hydronic zone valve.

A hydronic zone valve is used in hot water heating systems. In conjunction with your home’s thermostat, circulating pump and boiler, the hydronic zone valve helps control the flow of hot water through your hot water heating system.

Zone valves are fairly simple devices and as a result are frequently used in hot water heating systems. Typically multiple zone valves are used in a home heating system.

This allows multiple thermostats to be placed at different levels in the home or in different rooms of the house, so that you can independently control the heat to each level or room.

Zone valves are low voltage controlled via your thermostat. They are powered by a local 24V AC power supply source usually located near the boiler. When the thermostat turns on, the zone valve allows hot water to flow through the hot water heating system.

Unfortunately hydronic zone valves have the tendency to fail, and when they do fail, they frequently fail to the open position. When this happens the zone valve allows hot water to continuously flow through the hot water heating system, regardless of the thermostat setting. This causes the floor or room to heat up and the boiler to constantly run. When this happens you should turn the boiler off and call a plumbing or heating contractor.

Hydronic Zone Valve

In the event a hydronic zone valve fails closed, no hot water will flow through the system regardless of the thermostat setting. To mitigate this zone valve fail condition, plumbing/heating contractors frequently install multiple zone valves and circulator pumps into the hot water heating system. This solution helps to protect the house from freezing winter temperatures. If one of the hydronic zone valves fails, the other heating zones will still be operational and prevent the threat of frozen pipes. Again, if the zone valve fails closed, you should immediately call a plumber or heating contractor.

Repairing a hydronic zone valve can be quite straight forward. Many models are designed so that the valve does not need to be replaced. Instead the electric motor assembly, or powerhead, that makes up the upper portion of the hydronic zone valve can be swapped out with a replacement subassembly.


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